1. Field of the Invention
The present invention generally relates to a substrate for electrical device, and more particularly to a substrate which is enhancing the reliability of electrical device and downsizing an electrical device.
2. Description of the Related Art
Currently, both science and technology are developing rapidly, meanwhile, electrical devices are designed for thinner, wider application, lower cost, and better quality, wherein the better quality of electrical device includes higher reliability and enhanced heat dissipation, in order to achieve above objects, the manufacturers keep on developing it.
FIG. 17 shows a conventional electrical device 9 comprising a substrate 1 which including an insulator 30, a plurality of conductive elements 7,8 and a via 5, wherein said insulator 30 having a first upper surface 31 and a first lower surface 32, said first upper surface 31 of insulator 30 having an receiving area 4 which is used for accommodating a chip; said conductive element 7 is formed on said first upper surface 31 of insulator 30 and surrounding said receiving area 4, said conductive element 8 formed on said first lower surface 32 of insulator 30, said via 5 electrically connected the conductive element 7 to the conductive element 8, wherein said via 5 having a through hole 6 (i.e. the via 5 is hollow) in which an filler 43 such as solder paste, epoxy, glue or solder mask filled therein; a chip 20 mounted on the receiving area 4 of substrate 1; a conductive wire 60 electrically connected the chip 20 to the conductive element 7; an encapsulant 40 encapsulates the substrate 1, chip 20 and conductive wire 60, a solder ball 50 attached to the conductive element 8 for electrically connecting to the outside (e.g. a mother board); Accordingly, due to the solder ball 50, it is convenient for said electrical device 9 to be electrically connected to the outside, nevertheless, the cost of said electrical device 9 is increased, Moreover, the solder ball 50 is attached to the conductive element 8 by the surface 53 of the solder ball 50 exclusively, it is easy to cause peeling-off problems of said solder ball 50 by means of contamination which is happened while operating the attaching (solder ball) process, thermal effects and/or other reasons such as collision. When the peeling-off problem happened, the solder ball 50 separated from the conductive element 8 easily, it may cause the electrical device 9 not to be functional well. Furthermore, due to the via 5 is hollow, in this manner, it is easy to cause a crack problem “E” of said via 5 by means of thermal effects, when the crack “E” happened, the conductive element 7 will not be electrically connected to the conductive element 8 through said via 5 securely, then it will cause the electrical device 9 not to be functional well either; In addition, the conductive wire 60 electrically connected said chip 20 to said conductive element 7 of substrate 1 by means of a wire-bonding process, wherein said substrate 1 needs to be warm-up (i.e. heating; the temperature of heating is 140˜300° C.) in order to ensure the conductive wire 60 electrically connected said chip 20 to said conductive element 7 firmly, while operating a wire-bonding process, wherein although there is a filler (e.g. solder paste) 43 filled into the through hole 6 of the via 5 for reinforcing the strength of the via 5, however said filler (solder paste) 43 will become soft during the period of heating (due to the melting temperature of solder paste is about 183° C. usually), in this manner, said conductive wire 60 does not enable to be electrically connected to said via 5 directly, but needs to be electrically connected to the conductive element 7 instead, then it is necessary for the substrate 1 to be comprised of said conductive element 7, and then cost is increased, besides, the designation of said substrate 1 is restricted too.